Back contact solar cell and manufacturing method thereof

ABSTRACT

A back contact solar cell and a method for manufacturing the back contact solar cell are discussed. The back contact solar cell includes a substrate made of crystalline silicon having a first conductivity type, a passivation layer on one side of the substrate, an antireflection layer on the passivation layer, a first electrode on the other side of the substrate, a second electrode on the other side of the substrate and separated from the first electrode, a first semiconductor layer disposed between the first electrode and the substrate and having the first conductivity type, and a second semiconductor layer disposed between the second electrode and the substrate and having a second conductivity type that is opposite to the first conductivity type. The passivation layer includes at least one of amorphous silicon oxide and amorphous silicon carbide.

This application is a Divisional of copending U.S. application Ser. No.13/269,261, filed on Oct. 7, 2011, which claims priority under 35 U.S.C.§119(a) to Application No. 10-2010-0098925, filed in Korea on Oct. 11,2010, all of which are hereby expressly incorporated by reference intothe present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to a back contact solar cell and amethod for manufacturing the same and, more particularly, to a backcontact solar cell including a passivation layer having large bandgapenergy at a light receiving surface and a method for manufacturing thesame.

2. Description of the Related Art

Lately, alternative energy sources have been receiving greater attentionbecause it has been expected that traditional energy resources such asoil and coal will be depleted eventually. As the up and comingalternative energy source, a solar cell has drawing attention. The solarcell is also referred to as a next generation battery that employs asemiconductor element capable of directly converting solar light energyinto electric energy.

That is, the solar cell is a device that converts light energy intoelectric energy using the photovoltaic effect. Such a solar cell may beclassified into a silicon solar cell, a thin film solar cell, adye-sensitized solar cell (DSSC), and an organic polymer solar cell. Inorder to improve the performance of the solar cell, it is important toincrease the light-to-electric conversion efficiency of the solar cell.

A back contact solar cell includes electrodes formed at a rear sidethereof. Since all electrodes are arranged at the rear side, the backcontact solar cell can prevent loss of incident solar light, which maybe caused in a solar cell having electrodes arranged at a front sidethereof. Therefore, the back contact solar cell increases quantity ofabsorbed incident light. However, it is still important to increase thelight-to-electric conversion efficiency even for the back contact solarcell in order to further improve the performance thereof.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the invention is to solve at least theproblems and disadvantages of the related art.

In accordance with an aspect of the invention, a back contact solar cellincludes a substrate made of crystalline silicon having a firstconductivity type, a passivation layer on one side of the substrate, anantireflection layer on the passivation layer, a first electrode on theother side of the substrate, a second electrode on the other side of thesubstrate and separated from the first electrode, a first semiconductorlayer disposed between the first electrode and the substrate and havingthe first conductivity type, and a second semiconductor layer disposedbetween the second electrode and the substrate and having a secondconductivity type that is opposite to the first conductivity type. Thepassivation layer may include at least one of amorphous silicon oxideand amorphous silicon carbide.

The passivation layer may include a first layer on one side of thesubstrate, wherein the first layer includes amorphous silicon, and asecond layer on the first layer, wherein the second layer includes atleast one of amorphous silicon oxide and amorphous silicon carbide.

The passivation layer may have a bandgap energy of between about 1.8 eVand about 2.25 eV.

The first semiconductor layer may be an amorphous silicon layer havingan impurity concentration that is higher than that of the substrate.

The back contact solar cell may further include an intrinsic amorphoussemiconductor layer disposed between the substrate and the firstsemiconductor layer.

The second semiconductor layer may be an intrinsic amorphous siliconlayer for forming a hetero junction at an interface between the secondsemiconductor layer and the substrate.

The back contact solar cell may further include an intrinsic amorphoussemiconductor layer disposed between the substrate and the secondsemiconductor layer.

The antireflection layer may be a transparent electrode.

Each one of the first and second electrodes may include a transparentelectrode layer, and a metal layer on the transparent layer.

An uneven surface may be formed on one side of the substrate.

The back contact solar cell may further include a rear passivation layeron the other side of the substrate. The first electrode may contact thefirst semiconductor layer through the rear passivation layer, and thesecond electrode may contact the second semiconductor layer through therear passivation layer.

The rear passivation layer may be made of a material identical to thatof the passivation layer.

In accordance with another aspect of the invention, a back contact solarcell includes a substrate made of crystalline silicon having a firstconductivity type, a passivation layer on one side of the substrate, anantireflection layer on the passivation layer, a first electrode on theother side of the substrate, a second electrode on the other side of thesubstrate and separated from the first electrode, a first semiconductorlayer disposed between the first electrode and the substrate and havingthe first conductivity type, and a second semiconductor layer disposedbetween the second electrode and the substrate and having a secondconductivity type that is opposite to the first conductivity type. Thefirst and second semiconductor layers may be an amorphous silicon layer.The passivation layer may have a bandgap energy of between about 1.8 eVand about 2.25 eV.

The passivation layer may include at least one of amorphous siliconoxide and amorphous silicon carbide.

The passivation layer may include a first layer formed on one side ofthe substrate, wherein the first layer includes amorphous silicon, and asecond layer formed on the first layer, wherein the second layerincludes one of amorphous silicon oxide and amorphous silicon carbide.

In accordance with still another aspect of the invention, in order tomanufacture a back contact solar cell, a passivation layer is formed onone side of a substrate made of crystalline silicon and having a firstconductivity type. An antireflection layer is formed on the passivationlayer. Then, a first semiconductor layer having a first conductivitytype and a second semiconductor layer having a second conductivity typeare formed on the other side of the substrate at an interval. Afterforming the first and second semiconductor layers, first and secondelectrodes are formed on the first and second semiconductor layers,respectively. The first and second semiconductor layers may be made ofamorphous silicon, and the passivation layer is made of at least one ofamorphous silicon oxide and amorphous silicon carbide.

In the forming of the passivation layer, a first layer made of amorphoussilicon may be formed. Then, a second layer made of at least one ofamorphous silicon oxide and amorphous silicon carbide may be formed onthe first layer.

In the forming of the first second electrodes, a transparent electrodelayer and a metal layer may be formed sequentially.

The passivation layer may have a bandgap energy of between about 1.8 eVand about 2.25 eV.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in detail with referenceto the following drawings in which like numerals refer to like elements.

FIG. 1 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with an embodiment of theinvention.

FIG. 2 is a diagram that illustrates change of light absorptioncoefficients according to band-gap energy.

FIG. 3 illustrates J_(SC) of a back contact solar cell of FIG. 1, whichchanges according to a bandgap energy of a passivation layer.

FIG. 4 illustrates quantum efficiency (QE) of a back contact solar cellof FIG. 1, which changes according to a bandgap energy of a passivationlayer.

FIG. 5 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with another embodiment of theinvention.

FIG. 6 illustrates a method for manufacturing a back contact solar cellof FIG. 1.

FIG. 7 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with another embodiment of theinvention.

FIG. 8 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with yet another embodiment of theinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the drawings, it will be understood that when each constituentelement such as a layer, film, region, or substrate is referred to asbeing “on” or “under” another element, it can be directly on or underthe other element or it can be indirectly on or under the other element.Intervening elements may also be present. Furthermore, a top or a bottomof each constituent element may be described based on a top or a bottomof the drawings. In the drawings, each constituent element may beexaggerated, omitted, or schematically illustrated for betterunderstanding and ease of description. A size of each constituentelement may be different from the actual size thereof.

It is an object of the invention to provide a back contact solar cellfor improving light absorption, and a method for manufacturing the same.

Hereinafter, a back contact solar cell in accordance with an embodimentof the invention will be described with reference to accompanyingdrawings.

FIG. 1 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with an embodiment of theinvention. FIG. 2 is a diagram that illustrates change of lightabsorption coefficients according to band-gap energy. FIG. 3 illustratesJ_(SC) of a back contact solar cell of FIG. 1, which changes accordingto bandgap energy of a passivation layer. FIG. 4 illustrates quantumefficiency (QE) of a back contact solar cell of FIG. 1, which changesaccording to bandgap energy of a passivation layer.

Referring to FIG. 1, a back contact solar cell 100 includes a substrate110, such as a crystalline silicon substrate 110 having a firstconductivity type, a passivation layer 120 formed on one side of thesubstrate 110, an antireflection layer 130 on the passivation layer 120,a first electrode 150 on the other side of the substrate 110, and asecond electrode 160 on the other side of the substrate 110 andseparated from the first electrode 150.

The substrate 110 may be a crystalline silicon substrate having a firstconductive type. The substrate 110 may be doped with an n-type impurityor a p-type impurity. The substrate 110 may be a single crystallinesilicon substrate, a polycrystalline silicon substrate, or amicrocrystalline silicon substrate. The invention, however, is notlimited thereto.

One side of the substrate 110 may have an uneven surface in order tomaximize an area for absorbing incident light, such as solar light. Theuneven surface may also reduce a reflectivity of the solar light that isincident to the solar cell 100. Accordingly, the uneven surface mayincrease a catch rate (or retention rate) of incident light and reduceloss of the incident light to the solar cell 100.

The passivation layer 120 is formed on a light receiving side (alsoreferred to as one side, a front side or a front surface) of thesubstrate 110. The passivation layer 120 may reduce or preventrecombination of electrons and holes which result from electron-holepairs generated by the incident light. The passivation layer 120 mayalso reduce defects that may be caused when the antireflection layer 130is directly formed on the substrate 110. Such a passivation layer 120may include amorphous silicon oxide (a-SiO_(x)) or amorphous siliconcarbide (a-SiC). Other materials may be used for the passivation layer120.

FIG. 2 illustrates a light absorption coefficient changing according tobandgap energy. Referring to FIG. 2, it shows that amorphous siliconoxide (a-SiO_(x)) or amorphous silicon carbide (a-SiC) has a lightabsorption coefficient lower than that of amorphous silicon (a-Si)because a-SiO_(x) or a-SiC has bandgap energy greater than that of a-Si.The a-Si is generally used to form a typical passivation layer.

Since the passivation layer 120 is made of a-SiO_(x) or a-SiC that has alight absorption coefficient lower than that of a typical passivationlayer made of a-Si, the passivation layer 120 may absorb smallerquantity of solar light incident to the substrate 110, compared to thetypical passivation layer of a-Si. Therefore, the passivation layer 120may increase the quantity of solar light incident to the substrate 110.

Meanwhile, if a passivation layer is made of amorphous silicon (a-Si)having a large amount of hydrogen (H) added to improve its band-gapenergy, a plurality of pores may be generated. Such pores maydeteriorate the characteristics of the passivation layer. As a result,it is difficult to improve the bandgap energy to be more than about 1.8eV.

On the contrary, the passivation layer 120 including amorphous siliconoxide (a-SiO_(x)) or amorphous silicon carbide (a-SiC) may have abandgap energy that is higher than about 1.8 eV. Accordingly, the lightabsorption coefficient of the passivation layer 120 may be decreasedcompared to that of a typical passivation layer. For example, the lightabsorption coefficient is decreased to be lower than about 800 nm.

When bandgap energy of the passivation layer 120 is greater than about2.25 eV, the characteristics of the passivation layer 120 may bedeteriorated by added impurities. Accordingly, it is preferable, thoughnot required, to maintain the bandgap energy of the passivation layer120 at between about 1.8 eV and about 2.25 eV.

FIG. 3 illustrates J_(SC) of the back contact solar cell 100 of FIG. 1,which changes according to bandgap energy of the passivation layer 120.FIG. 4 illustrates quantum efficiency (QE) of the back contact solarcell 100 of FIG. 1, which changes according to the bandgap energy of thepassivation layer.

In FIG. 3, a curve formed along circle dots denotes the passivationlayer 120 formed of amorphous silicon oxide (a-SiO_(x)) or amorphoussilicon carbide (a-SiC). A curve formed along square dots denotes atypical passivation layer formed of a-Si. As shown in FIG. 3, thepassivation layer 120 formed of a SiO_(x) or a SiC has a bandgap energyat between about 1.85 eV and about 2.25 eV. The typical passivationlayer formed of a-Si has a bandgap energy lower than about 1.75 eV. FIG.3 illustrates J_(SC) of the back contact solar cell 100 including thepassivation layer 120 and J_(SC) of a back contact solar cell having atypical passivation layer.

As shown in FIG. 3, the passivation layer 120 formed of amorphoussilicon oxide (a-SiO_(x)) or amorphous silicon carbide (a-SiC) hasJ_(SC) higher than that of the typical passivation layer formed of a-Si.Accordingly, an amount of light absorbed by the passivation layer 120 isreduced compared to that of the typical passivation layer. At the sametime, recombination current is effectively suppressed in the passivationlayer 120.

Referring to FIG. 4, as the bandgap energy of the passivation layer 120increases, QE (quantum efficiency) also increases. Accordingly, thelight-to-electric conversion efficiency of the solar cell 100 increasesdue to the increment of the quantity of light incident to the solar cell100.

Referring to FIG. 1 again, the antireflection layer 130 may be disposedon the passivation layer 120 in order to reduce reflection of solarlight that is incident on the front surface of the substrate 110.

When the reflection of the solar light is reduced as described above,the quantity of light reaching a p-n junction of the solar cell 100increases and the light-to-electric conversion efficiency of the solarcell 100 may be improved.

For example, the antireflection layer 130 may be formed as a singlelayer selected from the group consisting of a silicon nitride layer, asilicon nitride layer having hydrogen, a silicon oxide layer, a siliconoxynitride layer, MgF₂, ZnS, TiO₂, and CeO₂, or formed as amulti-layered structure including at least two layers selected from thegroup. The antireflection layer 130 may be formed by vapor deposition,chemical vapor deposition, spin coating, screen printing, or spraycoating. The invention, however, is not limited thereto.

With reference back to FIG. 1 and in accordance with an embodiment ofthe invention, the back contact solar cell 100 may include a firstelectrode 150 and a second electrode 160. The first electrode 150 andthe second electrode 160 are formed on a side of the substrate 110,which faces the front side where the passivation layer 120 is formedthereon. The first electrode 150 and the second electrode 160 areseparated from each other. The side of the substrate 110 which faces thefront side of the substrate 110 may also be referred to as the otherside, a back side or a back surface of the substrate 110.

The back contact solar cell 100 may further include a firstsemiconductor layer 140 disposed between the substrate 110 and the firstelectrode 150, and a second semiconductor layer 141 between thesubstrate 110 and the second electrode 160. The first semiconductorlayer 140 may have a first conductivity type, and the secondsemiconductor layer 141 may have a second conductivity type that isopposite to the first conductivity type.

The first semiconductor layer 140 and the second semiconductor layer 141may be an amorphous silicon (a-Si) layer or may be doped with an n-typeimpurity or a p-type impurity.

As described above, the first and second semiconductor layers 140 and141 may form a hetero junction with the crystal substrate 110 becausethe first and second semiconductor layers 140 and 141 are made of theamorphous silicon (a-Si) layer. Accordingly, a bandgap increases at aninterface of the substrate 110, and an open circuit voltage (Voc) of thesolar cell 100 may be improved.

The substrate 110 may be doped with an n-type impurity or a p-typeimpurity, and may have a first conductivity type. For example, when thesubstrate 110 is an n-type silicon substrate, the first semiconductorlayer 140 may include the same conductivity type impurity and a higherimpurity concentration compared to those of the substrate 110. In thisinstance, the first semiconductor layer 140 may collect electronsobtained by way of the photoelectric effect of the solar cell 100.

Furthermore, the second semiconductor layer 141 may be doped with asecond conductivity type impurity that is opposite to the firstconductivity type. Accordingly, the second semiconductor layer 141 maycollect holes. A p-n junction may be formed at an interface between thesubstrate 110 and the second semiconductor layer 141.

On the contrary, when the substrate 110 is a p-type silicon substrate,the first semiconductor layer 140 may collect holes since the firstsemiconductor layer 140 includes the same conductivity type impurity anda higher impurity concentration compared to those of the substrate 110.

The solar cell 100 may optionally include an intrinsic amorphous siliconlayer 140 a, 141 a between the substrate 110 and at least one of thefirst and second semiconductor layers 140 and 141 (see FIG. 7). Theintrinsic amorphous silicon layer may be formed on an entire bottom side(or the back side) of the substrate 110. Alternatively, the intrinsicamorphous silicon layer 140 a, 141 a may be formed at only areas wherethe first and second semiconductor layers 140 and 141 are formed (seeFIG. 7), or at areas that include the first and second semiconductorlayers 140 and 141 either fully or partially. The first electrode 150may electrically contact the first semiconductor layer 140, and thesecond electrode 160 may electrically contact the second semiconductorlayer 141. Accordingly, the first and second electrodes 150 and 160 maytransfer electrons and holes collected at the first and secondsemiconductor layers 140 and 141 to the outside.

The first and second electrodes 150 and 160 may include transparentelectrode layers 151 and 161 and metal layers 153 and 163, respectively.For convenience and ease of understanding, the first electrode 150 willbe representatively described, hereinafter. However, description of thefirst electrode 150 may be equally applied to the second electrode 160.

The transparent electrode layer 151 may be made of a transparentconductive oxide (TCO). The transparent electrode layer 151 may improveadhesiveness between the first semiconductor layer 140 made of amorphoussilicon and the metal layer 153 made of metal. The transparent electrodelayer 151 may include at least one of ITO, IZO (In—ZnO), GZO (Ga—ZnO),AZO (Al—ZnO), AGZO (Al—Ga ZnO), IGZO (In—Ga ZnO), IrOx, RuOx, RuOx/ITO,Ni/IrOx/Au, and Ni/IrOx/Au/ITO, but the embodiments of the invention arenot limited thereto.

The metal layer 153 on the transparent electrode layer 151 may reduceresistance for the first electrode 150 and may be electrically connectedto an external terminal or an external circuit. The metal layer 153 maybe made of metal having low electric resistance, such as gold, silver,copper, or aluminum. However, embodiments of the invention are notlimited thereto.

An insulation layer may optionally be formed between the first electrode150 and the second electrode 160. The insulation layer may prevent thefirst electrode 150 and the second electrode 160 from being shorted.

In accordance with an embodiment of the invention, the back contactsolar cell 100 may further include a rear passivation layer on the otherside (or the back side) of the substrate 110. For example, the rearpassivation layer may be formed on a top side (or an exposed surface) ofthe first and second semiconductor layers 140 and 141 when the first andsecond semiconductor layers 140 and 141 are continuously formed.Furthermore, the rear passivation layer may be formed on the other sideof the substrate 110 and be located between the first and secondsemiconductor layers 140 and 141, as well as on the top side of thefirst and second semiconductor layers 140 and 141 when the first andsecond semiconductor layers 140 and 141 are formed at an interval (i.e.,are separated).

In accordance with an embodiment of the invention, the back contactsolar cell 100 may further include a rear passivation layer 122 (seeFIG. 8) on the other side (or the back side) of the substrate 110. Forexample, the rear passivation layer may be formed on a top side (or anexposed surface) of the first and second semiconductor layers 140 and141 when the first and second semiconductor layers 140 and 141 arecontinuously formed. Furthermore, the rear passivation layer may beformed on the other side of the substrate 110 and be located between thefirst and second semiconductor layers 140 and 141, as well as on the topside of the first and second semiconductor layers 140 and 141 when thefirst and second semiconductor layers 140 and 141 are formed at aninterval (i.e., are separated).

When the solar cell 100 includes the rear passivation layer, the firstand second electrodes 150 and 160 may penetrate through the rearpassivation layer and contact the first and second semiconductor layers140 and 141.

FIG. 5 is a cross-sectional view that illustrates a cross-section of aback contact solar cell in accordance with another embodiment of theinvention.

Referring to FIG. 5, the back contact solar cell 200 includes asubstrate 210, a passivation layer 220 on one side of the substrate 210,an antireflection layer 230 on the passivation layer 220, and first andsecond electrodes 250 and 260 formed on the other side of the substrate210. The back contact solar cell 200 further includes first and secondsemiconductor layers 240 and 241 between the substrate 210 and the firstand second electrodes 250 and 260, respectively.

Since the substrate 210, the antireflection layer 230, the first andsecond electrodes 250 and 260, and the first and second semiconductorlayers 240 and 241 are identical to those shown in FIG. 1, the detaileddescriptions thereof will be omitted herein.

Referring to FIG. 5, the passivation layer 220 may include a first layer222 and a second layer 224 formed on the first layer 222. The firstlayer 222 may be made of amorphous silicon (a-Si), and the second layer224 may be made of amorphous silicon oxide (a-SiO_(x)) or amorphoussilicon carbide (a-SiC).

In a manner shown in FIG. 1, the second layer 224 also includesamorphous silicon oxide (a-SiO_(x)) or amorphous silicon carbide(a-SiC). Accordingly, the bandgap energy of the passivation layer 220 isimproved, and quantity of light absorbed into the passivation layer 220may be reduced.

The density of electrons and holes generated at the solar cell 200 maybe concentrated at a front surface of the substrate 210 and may begeometrically reduced along the depth of the substrate 210. In order toreduce or prevent this phenomenon, the first layer 222 made of a-Si maybe formed on the substrate 210 in accordance with an embodiment of theinvention. Accordingly, recombination of electron and hole may befurther effectively reduced or prevented.

FIG. 6 illustrates a method for manufacturing a back contact solar cellof FIG. 1.

Referring to FIG. 6, one side of the substrate 110 may be textured asshown in a diagram (a) of FIG. 6. As a result, an uneven surface isformed at the one side of the substrate 110. After the texturingprocess, a passivation layer 120 and an antireflection layer 130 aresequentially formed on the uneven surface of the substrate 110.

The texturing process may form an uneven pattern at a surface of thesubstrate 110. If the uneven pattern is formed on the surface of thesubstrate 110 through the texturing process, reflectivity of incidentlight becomes reduced and a catch rate (or retention rate) of incidentlight becomes increased. Therefore, loss of incident light may bereduced.

When the uneven pattern is formed through the texturing process, thepassivation layer 120 and the antireflection layer 130 may besequentially formed on the substrate 110 along the uneven pattern of thesubstrate 110. As a result, the passivation layer 120 and theantireflection layer 130 may also have an uneven pattern.

As the texturing process, the substrate 110 may be immersed in anetching solution. The uneven pattern may be formed in various shapessuch as a pyramid, rectangle, and triangle.

The passivation layer 120 may be formed through one of sputtering,e-beam evaporation, chemical vapor deposition (CVD), physical vapordeposition (PDV), metal-organic chemical vapor deposition (MOCVD),molecular beam epitaxial (MBE), and Atomic Layer Deposition.

Meanwhile, the passivation layer 120 may include amorphous silicon oxide(a-SiO_(x)) or amorphous silicon carbide (a-SiC). Accordingly, thepassivation layer 120 may have a bandgap energy higher than about 1.8eV, preferably between about 1.8 and about 2.25 eV. Therefore, thepassivation layer 120 reduces or prevents incident light from beingabsorbed into the passivation layer 120. Finally, the quantity of lightthat is incident to the substrate 110 may be increased.

As described in FIG. 5, the passivation layer 120 may include a firstlayer and a second layer. The first layer may be made of amorphoussilicon (a-Si), and the second layer may be made of one of amorphoussilicon oxide (a-SiO_(x)) and amorphous silicon carbide (a-SiC). Whenthe passivation layer 120 further includes the first layer made of a-Si,electron and hole recombination can be effectively reduced or prevented.

The antireflection layer 130 may be formed through one of sputtering,e-beam evaporation, chemical vapor deposition (CVD), physical vapordeposition (PDV), and Atomic Layer Deposition. However, embodiments ofthe invention are not limited thereto.

As shown in diagrams (b) and (c), an amorphous silicon (a-Si) layerincluding p-type or n-type impurity may be formed on the other side (theback side) of the substrate 110, and a second semiconductor layer 141 isformed by patterning the a-Si layer.

In the patterning process, a photo-resist layer having an opening isdisposed corresponding to the second semiconductor layer 141, and anexposing process, a developing process, and an etching process aresequentially carried out.

As shown in diagrams (d) and (e), an amorphous silicon (a-Si) layerhaving a n-type or a p-type impurity is formed entirely on the otherside of the substrate 110 to have the opposite conductivity type of thesecond semiconductor layer 141. Then, a first semiconductor layer 140 isformed by patterning the a-Si layer.

The patterning process for forming the first semiconductor layer 140 maybe identical to that for forming the second semiconductor layer 141.FIG. 6 illustrates that the first semiconductor layer 140 is formedafter the second semiconductor layer 141 is formed. However, embodimentsof the invention are not limited thereto. The first semiconductor layer140 may be formed first before the second semiconductor layer 141 isformed.

An intrinsic amorphous semiconductor layer contacting the substrate 110may be formed before forming the first and second semiconductor layers140 and 141. The intrinsic amorphous semiconductor layer may be formedentirely on a bottom side of the substrate 110. Alternatively, theintrinsic amorphous semiconductor layer may be formed on only areascorresponding to the first and second semiconductor layers 140 and 141.

As shown in diagram (f) of FIG. 6, the first and second electrodes 150and 160 may be formed on the first and second semiconductor layers 140and 141, respectively.

The first and second electrodes 150 and 160 may include transparentelectrode layers 151 and 161 and metal electrode layers 153 and 163,respectively.

The transparent electrode layers 151 and 161, and the metal electrodelayers 153 and 163 may be formed by disposing a mask having openingscorresponding to areas for forming the transparent electrode layers 151and 161 and metal electrode layers 153 and 163, and then carrying outone of sputtering, e-beam evaporation, chemical vapor deposition (CVD),physical vapor deposition (PDV), metal-organic chemical vapor deposition(MOCVD), molecular beam epitaxial (MBE), and Atomic Layer Deposition.

A rear passivation layer may be formed on the other side of thesubstrate 110 before forming the first and second electrodes 150 and160. The rear passivation layer may be made of the same material as thatof the passivation layer 120.

The rear passivation layer may be formed by: i) depositing a rearpassivation layer on the other side of the substrate 110; ii) forming amask layer having openings located on the top areas (or exposed areas)of the first and second semiconductor layers 140 and 141; and iii)forming openings at the rear passivation layer using the mask layer andremoving the mask.

The first and second electrodes 150 and 160 may contact the first andsecond semiconductor layers 140 and 141 through the openings of the rearpassivation layer.

Embodiments of the invention are not limited to configurations of theabove described embodiments. That is, a back contact solar cell inaccordance with an embodiment of the invention may be modified invarious ways. For example, a back contact solar cell may include theentire configuration of one of the above described embodiments orselectively include predetermined parts of corresponding embodiments.

The foregoing embodiments and aspects of the invention are merely forexample and are not to be construed as limiting the invention. Theteaching can be readily applied to other types of apparatuses. Also, thedescription of the exemplary embodiments of the invention is intended tobe illustrative, and not to limit the scope of the claims, and manyalternatives, modifications, and variations will be apparent to thoseskilled in the art.

What is claimed is:
 1. A back contact solar cell comprising: a substratemade of crystalline silicon having a first conductivity type; apassivation layer on one side of the substrate; an antireflection layeron the passivation layer; a first electrode on the other side of thesubstrate; a second electrode on the other side of the substrate andseparated from the first electrode; a first semiconductor layer disposedbetween the first electrode and the substrate and having the firstconductivity type; and a second semiconductor layer disposed between thesecond electrode and the substrate and having a second conductivity typethat is opposite to the first conductivity type, wherein the first andsecond semiconductor layers are an amorphous silicon layer, and thepassivation layer has a bandgap energy of between about 1.8 eV and about2.25 eV.
 2. The back contact solar cell of claim 1, wherein thepassivation layer includes at least one of amorphous silicon oxide andamorphous silicon carbide.
 3. The back contact solar cell of claim 1,wherein the passivation layer comprises: a first layer formed on the oneside of the substrate, wherein the first layer includes amorphoussilicon; and a second layer formed on the first layer, wherein thesecond layer includes one of amorphous silicon oxide and amorphoussilicon carbide.
 4. A method for manufacturing a back contact solarcell, the method comprising: forming a passivation layer on one side ofa substrate made of crystalline silicon and having a first conductivitytype; forming an antireflection layer on the passivation layer; forminga first semiconductor layer having a first conductivity type and asecond semiconductor layer having a second conductivity type on theother side of the substrate at an interval; and forming first and secondelectrodes on the first and second semiconductor layers, respectively,wherein the first and second semiconductor layers are made of amorphoussilicon, and the passivation layer is made of at least one of amorphoussilicon oxide and amorphous silicon carbide.
 5. The method of claim 4,wherein the forming of the passivation layer comprises: forming a firstlayer made of amorphous silicon; and forming a second layer made of atleast one of amorphous silicon oxide and amorphous silicon carbide onthe first layer.
 6. The method of claim 4, wherein the forming of thefirst second electrodes comprises: forming a transparent electrode layerand a metal layer sequentially.
 7. The method of claim 4, wherein thepassivation layer has a bandgap energy of between about 1.8 eV and about2.25 eV.